1. Field of the Invention
The present invention relates to an automatic transmission for vehicles. More particularly, the present invention relates to a planetary gear train of an automatic transmission of a vehicle which improves power delivery performance and reduces fuel consumption by achieving eleven forward speed stages using a minimum number of constituent elements.
2. Description of Related Art
In recent years, a rise in oil price causes a rise in competition for technologies to enhance fuel efficiency.
As a result, research into reduction of weight and enhancement of fuel efficiency through down-sizing is being conducted in the case of an engine and research for simultaneously securing operability and fuel efficiency competitiveness through multi-stages is being conducted in the case of an automatic transmission.
However, in the automatic transmission, as a transmission stage increases, the number of internal components increases, and as a result, mountability, transmission efficiency, and the like may still deteriorate and cost, and weight may increase.
Accordingly, development of a planetary gear train which may bring about maximum efficiency with as small a number of components may be important in order to increase a fuel efficiency enhancement effect through the multi-stages.
In this aspect, in recent years, 8 and 9-speed automated transmissions tend to be achieved and the research and development of a planetary gear train capable of implementing more transmission stages has also been actively conducted.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.